The invention relates to a method of assessing the effect of yarn defects on textile fabrics, by simulating an image of the fabric based on a predetermined yarn.
Such a method is known from EP-A-578975 and related U.S. Pat. No. 5,671,061in which in a first step a yarn is examined by a measuring element with respect to parameters which are connected with the volume and/or the surface of the yarn. In a second step the parameters are converted into grey or color values and these values are associated with pixels. Finally the pixels are reproduced on a display screen and/or a printer. An image is thereby generated which represents a simulation of a woven or knitted fabric produced from the examined yarn.
A disadvantage of the known method consists in the fact that this simulation does not correspond precisely to the image of an actual woven or knitted fabric, since simplifying assumptions are made for the purpose of simulation, which assumptions have the above effect. Such an assumption comprises representing in the simulation yam portions lying parallel with each other and weighting or even completely ignoring cross-weaving between warp and weft yams. Thus, the assessment of a simulated woven or knitted fabric is made more difficult. Correct assessment therefore requires a certain amount of practice.
The object which the invention is intended to achieve comprises removing the above-mentioned disadvantages and providing a method with which assessment of simulated textiles fabrics may be effected with greater certainty.
The object is achieved in that an image of a woven or knitted fabric, which has arisen through known simulation, wherein parameters of a real, measured yarn are taken into consideration, is compared with the image of a woven or knitted reference fabric for which the parameters used are those of a reference yarn standardized according to quality or graded according to statistical data. The reference yam is characterized by parameters which correspond, for example, to average values such as may be inferred from published statistics. The parameters of the reference yam may thus be obtained by measuring a real reference yarn or by calculation from given statistical values.
In other words, an image of a woven reference fabric is produced which is more like the image of the fabric woven from given yam and with which the image of the known simulated woven fabric may be compared. The image of the woven reference fabric may be achieved by mapping a so called yarn diagram, which is compiled with a reference yarn. Or, the image of the reference yarn may be generated by simulation of a woven fabric from the reference yarn. Simulation of the reference yarn may be effected by calculation of yarn parameters or by measuring the parameters of a real reference yarn. The best result is achieved if two textile fabrics are simulated in the same way, wherein the only difference is in the values for the parameters, wherein one series of values originates from a given yarn and the other values from a reference yarn.
The advantages achieved by the invention are in particular that the woven or knitted reference fabric is represented in precisely the same manner as the simulated woven or knitted fabric on a screen or on paper, such that deviations between the images directly indicate deviations between real knitted and woven fabrics and as a result different values are considered for the selected parameters. For these directly comparable images, the observer, who has to assess these, may also apply his own subjective criteria, which he may use for assessment. He need not fear any distortion of his criteria, as would have to be taken into account when the images are not directly comparable.